Cyanoethylethers are widely used as a feedstock for the production of primary amines. These cyanoethylethers are commonly produced by the reaction of acrylonitrile or methacrylonitrile with an alcohol. Diaminopropyldiethyleneglycol (DAPDEG) is a valuable diprimary amine produced by a two step process involving the cyanoethylation of diethylene glycol followed by hydrogenation of the thus formed bis(2-cyanoethyl)diethylene glycol. One of the problems encountered during the hydrogenation of cyanoethylated alcohols, and, particularly in the hydrogenation of bis(2-cyanoethyl)diethyleneglycol, is the continuous loss of catalyst activity and selectivity to the product.
The following patents and articles are representative of the art in the cyanoethylation of alcohols such as glycols.
U.S. Pat. No. 4,313,004 discloses the hydrogenation of cyanoethers in the presence of ammonia and sodium hydroxide over a nickel catalyst at elevated pressures (800-2000 psig) and temperatures of 90-160° C. It is suggested that the hydrogenation may be carried out in the presence or absence of a solvent. To minimize cleavage, the nitrile is added incrementally to the hydrogenation reactor. High yields of diamines (95-98%) are obtained.
U.S. Pat. No. 5,869,653 disloses a process for the catalytic hydrogenation of nitrites formed by the cyanoethylation of glycols or the cyanoethylation of amines in the presence of a sponge or Raney cobalt catalyst. Lithium hydroxide is added to achieve high rates of primary amine formation.
U.S. Pat. No. 5,075,507 discloses a process for the separation of unreacted acrylonitrile in a process for the cyanoethylation of glycols. In the process, a primary of secondary amine is added to the reaction medium. The process may be carried out in the presence or absence of a solvent which solvents include alcohols and hydrocarbons.